There is a critical need that the mechanisms of wear in marine components sliding under marginally-lubricated conditions be elucidated. These conditions were simulated in a tribotester that was operated under conditions of high nominal pressure, low speed, and small-amplitude reciprocating sliding. High purity (99.9%) copper was selected as the rubbing member because of its relatively simple microstructure and its widespread use as a base metal in many bearing alloys. The friction and wear of this metal, rubbing against various counterfaces in 'inert' mineral oil, were determined. Topographical changes and subsurface deformation structures produced by sliding were determined. The investigation produced information on the following: The influence of topographical changes on the coefficient of friction (or frictional force); The dependence of the depth of deformation on the coefficient of friction; The mechanism of wear particle formation; and The relationship between wear and the coefficient of friction. The results also suggested that the topographical changes produced by sliding may be more important than the properties of the material itself in determining wear resistance.